Core cowl airfoil for a gas turbine engine

ABSTRACT

An example core nacelle for a gas turbine engine includes a core cowl positioned adjacent an inner duct boundary of a fan bypass passage and having a pocket and an airfoil received within the pocket. The airfoil is moveable between a first position and a second position to adjust a discharge airflow cross-sectional area of the gas turbine engine.

BACKGROUND OF THE INVENTION

This invention generally relates to a gas turbine engine, and moreparticularly to a turbofan gas turbine engine having a core cowlincluding an airfoil for increasing a discharge airflow cross-sectionalarea of the gas turbine engine.

In an aircraft gas turbine engine, such as a turbofan engine, air ispressurized in a compressor and mixed with fuel and burned in acombustor for generating hot combustion gases. The hot combustion gasesflow downstream through turbine stages that extract energy from thegases. A high pressure turbine powers the compressor, while a lowpressure turbine powers a fan disposed upstream of the compressor.

Combustion gases are discharged from the turbofan engine through a coreexhaust nozzle, and fan air is discharged through an annular fan exhaustnozzle defined at least partially by a fan nacelle surrounding the coreengine. A significant amount of propulsion thrust is provided by thepressurized fan air which is discharged through the fan exhaust nozzle.The combustion gases are discharged through the core exhaust nozzle toprovide additional thrust.

A significant amount of the air pressurized by the fan bypasses theengine for generating propulsion thrust in turbofan engines. High bypassturbofans typically require large diameter fans to achieve adequateturbofan engine efficiency. Therefore, the nacelle of the turbofanengine must be large enough to support the large diameter fan of theturbofan engine. Disadvantageously, the relatively large size of thenacelle results in increased weight, noise and drag that may offset thepropulsive efficiency achieved by the high bypass turbofan engine.

It is known in the field of aircraft gas turbine engines that theperformance of the turbofan engine varies during diverse flightconditions experienced by the aircraft. Typical turbofan engines aredesigned to achieve maximum performance during normal cruise operationof the aircraft. Therefore, when combined with the necessity of arelatively large nacelle size, increased noise and decreased efficiencymay be experienced by the aircraft at non-cruise operability conditionssuch as take-off, landing, cruise maneuver and the like.

Accordingly, it is desirable to provide a turbofan engine having avariable discharge airflow cross-sectional area that achieves noisereductions and improved fuel economy in a relatively inexpensive andnon-complex manner.

SUMMARY OF THE INVENTION

An example core nacelle for a gas turbine engine includes a core cowlpositioned adjacent an inner duct boundary of a fan bypass passage andhaving a pocket and an airfoil received within the pocket. The airfoilis moveable between a first position and a second position to adjust adischarge airflow cross-sectional area of the gas turbine engine.

An example nacelle assembly for a gas turbine engine includes a fannacelle, a core nacelle within the fan nacelle that includes a core cowlhaving an airfoil, a sensor that detects an operability condition, and acontroller in communication with the sensor to move the airfoil betweena first position and a second position. The airfoil is received within apocket of the core cowl and is positioned adjacent to a fan exhaustnozzle in the first position. The airfoil is moved to the secondposition to achieve a discharge airflow cross-sectional area greaterthan the discharge airflow cross-sectional area of the first position inresponse to detecting the operability condition.

An example method of increasing the discharge airflow cross-sectionalarea of a gas turbine engine includes sensing an operability conditionand translating a core cowl airfoil in an aft direction of the gasturbine engine in response to detecting the operability condition. Inone example, the operability condition includes a take-off condition.

The various features and advantages of this invention will becomeapparent to those skilled in the art from the following detaileddescription. The drawings that accompany the detailed description can bebriefly described as follows.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a general perspective view of an example gas turbineengine;

FIG. 2 is a schematic view of an example gas turbine engine having acore cowl including an airfoil moveable between a first position and asecond position;

FIG. 3 illustrates an example actuator assembly for moving the airfoilbetween the first position and the second position; and

FIG. 4 is a schematic view of an example gas turbine engine having acore cowl including an airfoil moveable between a first position and athird position that is different than the second position illustrated inFIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1, a gas turbine engine 10 suspends from an enginepylon 12 as is typical of an aircraft designed for subsonic operation.In one example, the gas turbine engine is a geared turbofan aircraftengine. The gas turbine engine 10 includes a fan section 14, a lowpressure compressor 15, a high pressure compressor 16, a combustor 18, ahigh pressure turbine 20 and a low pressure turbine 22. A low speedshaft 19 rotationally supports the low pressure compressor 15 and thelow pressure turbine 22 and drives the fan section 14 through a geartrain 23. A high speed shaft 24 rotationally supports the high pressurecompressor 16 and a high pressure turbine 20. The low speed shaft 19 andthe high speed shaft 24 rotate about a longitudinal centerline axis A ofthe gas turbine engine 10.

During operation, air is pressurized in the compressors 15, 16 and mixedwith fuel and burned in the combustor 18 for generating hot combustiongases. The hot combustion gases flow through the high and low pressureturbines 20, 22 which extract energy from the hot combustion gases.

The example gas turbine engine 10 is in the form of a high bypass ratio(i.e., low fan pressure ratio geared) turbofan engine mounted within afan nacelle 26, in which most of the air pressurized by the fan section14 bypasses the core engine itself for the generation of propulsionthrust. The example illustrated in FIG. 1 depicts a high bypass flowarrangement in which approximately 80 percent of the airflow enteringthe fan nacelle 26 may bypass the core nacelle 28 via a fan bypasspassage 27. The high bypass flow arrangement provides a significantamount of thrust for powering the aircraft.

In one example, the bypass ratio is greater than 10, and the fan section14 diameter is substantially larger than the diameter of the lowpressure compressor 15. The low pressure turbine 22 has a pressure ratiothat is greater than 5, in one example. The gear train 23 can be anyknown gear system, such as a planetary gear system with orbiting planetgears, planetary system with non-orbiting planet gears, or other type ofgear system. In the disclosed example, the gear train 23 has a constantgear ratio. It should be understood, however, that the above parametersare only exemplary of a contemplated geared turbofan engine. That is,the invention is applicable to other engine architectures.

Fan discharge airflow F1 is discharged from the engine 10 through a fanexhaust nozzle 30, defined radially between a core nacelle 28 and thefan nacelle 26. Core exhaust gases C are discharged from the corenacelle 28 through a core exhaust nozzle 32 defined between the corenacelle 28 and a tail cone 34 disposed coaxially therein around thelongitudinal centerline axis A of the gas turbine engine 10.

The fan exhaust nozzle 30 concentrically surrounds the core nacelle 28near an aft most segment 29 of the fan nacelle 26. The fan exhaustnozzle 30 defines a discharge airflow cross-sectional area 36 associatedwith the fan bypass passage 27 between the fan nacelle 26 and the corenacelle 28 for axially discharging the fan discharge airflow F1pressurized by the upstream fan section 14.

FIG. 2 illustrates an example core cowl 38 of the core nacelle 28 of thegas turbine engine 10. The core cowl 38 is an exterior flow surface of asection of the core nacelle 28. The core cowl 38 is positioned adjacentan inner duct boundary 25 of the fan bypass passage 27. The example corecowl 38 includes a pocket 40 for receiving an airfoil 42 near a top sideof the core nacelle 28. Although the pocket 40 and the airfoil 42 areillustrated at the top side of the core nacelle, it should be understoodthat additional locations of the core nacelle could have a similarconfiguration. In one example, the airfoil 42 is at least partiallyreceived within the pocket 40 adjacent to the fan exhaust nozzle 30. Theactual size and shape of the airfoil 42 and the pocket 40 of the corecowl 38 will vary depending upon design specific parameters including,but not limited to, the size of the core nacelle 28 and the efficiencyrequirements of the gas turbine engine 10.

In the illustrated example, the discharge airflow cross-sectional area36 extends within the fan bypass passage 27 between the aftmost segment29 of the fan nacelle 26 adjacent the fan exhaust nozzle 30 and an uppersurface 46 of the airfoil 42. Varying the discharge airflowcross-sectional area 36 of the gas turbine engine 10 during specificflight conditions provides noise reductions and improved fuelconsumption of the gas turbine engine 10. In one example, the dischargeairflow cross-sectional area 36 is varied by translating the airfoil 42aft from its stored position within the pocket 40. The airfoil 42 ismoved from a first position X (i.e., the stored position within thepocket 40, represented by solid lines) to a second position X′(represented by phantom lines) in response to detecting an operabilitycondition of the gas turbine engine 10. A discharge airflowcross-sectional area 48 of the second position X′ is greater than thedischarge airflow cross-sectional area 36 of the first position X. Inone example, the operability condition includes a take-off condition.However, the airfoil 42 may be translated between the first position Xand the second position X′ in response to any known operabilitycondition, such as landing or cruise.

A sensor 52 detects the operability condition and communicates with acontroller 54 to translate the airfoil 42 between the first position Xand the second position X′ via an actuator assembly 56. Of course, thisview is highly schematic. It should be understood that the sensor 52 andthe controller 54 are programmable to detect known flight conditions. Aperson of ordinary skill in the art having the benefit of the teachingsherein would be able to program the controller 54 to communicate withthe actuator assembly 56 to translate the airfoil 42 between the firstposition X and the second position X′. The distance the airfoil 42translates in response to detecting the operability condition will varydepending on design specific parameters. The actuator assembly 56 movesthe airfoil 42 from the second position X′ to the first position Xwithin the pocket 40 during normal cruise operation (e.g., a generallyconstant speed at generally constant, elevated altitude) of theaircraft.

A secondary airflow passage 62 in addition to the fan bypass passage 27extends between the airfoil 42 and the core exhaust nozzle 32 when theairfoil 42 is positioned at the second position X′. The secondaryairflow passage 62 provides an additional passage for fan airflow F1that in turn provides acoustic benefits. The secondary airflow passage62 provides acoustic changes of the fan airflow F1 through the fanbypass passage 27.

The second discharge airflow cross-sectional area 48 permits anincreased amount of fan airflow F1 to exit the fan exhaust nozzle 30 ascompared to the first discharge airflow cross-sectional area 36.Therefore, the fan section 14 design is optimized for diverseoperability conditions to achieve noise reductions and maximize fueleconomy.

FIG. 3 illustrates an example actuator assembly 56 mounted within acavity 61 of the core nacelle 28, for example. In another example, theactuator assembly 56 is mounted to the core cowl 38. The actuatorassembly 56 extends the airfoil 42 between the first position X and thesecond position X' in response to detecting the operability condition.In one example, the actuator assembly 56 comprises a hydraulicallyextendable rod 64. In another example, the actuator assembly 56comprises an electrically extendable rod. In yet another example, theactuator assembly 56 is a ball screw. A worker of ordinary skill in theart with the benefit of the teachings herein would understand how toextend the airfoil 42 between the first position X and the secondposition X′. One example pocket 40 of the core cowl 38 is designedslightly larger than the airfoil 42 to provide clearance for thetranslation of the airfoil 42 between the first position X and thesecond position X′.

FIG. 4 illustrates another example arrangement of the airfoil 42. Theairfoil 42 is pivotally mounted within the pocket 40 of the core cowl 38with a pivot mount 60, for example. In one example, the pivot mount is ahinge pin. Other types of mounts may also be used to attach the airfoil42 to the core cowl 38. The pivot mount 60 is located near a trailingedge 66 of the airfoil 42, in one example. However, the pivot mount 60may be located anywhere on the airfoil 42. A worker of ordinary skill inthe art with the benefit of the teachings herein would be able topivotally mount the airfoil 42 within the pocket 40.

The airfoil 42 is pivotable between the first position X within thepocket 40 and another position Y (represented by phantom lines) byrotating the airfoil 42 about the pivot mount 60. In one example, theposition Y is different than the second position X′. The pocket 40 isdesigned and sized to provide clearance for the rotational movement ofthe airfoil 42 between the first position X and the position Y. A workerof ordinary skill in the art with the benefit of this disclosure wouldunderstand how to design the pocket 40 to allow rotational movement ofthe airfoil 42.

Positioning the airfoil 42 at the position Y provides the gas turbineengine 10 with a thrust spoiling feature. In the position Y, the airfoil42 temporarily diverts the fan airflow F1 such that the fan airflow F1is blown in a forward direction to provide a thrust reversing force thatacts against the forward travel of the aircraft, providing deceleration.

In one example, the airfoil 42 is pivoted to the position Y in responseto an approach condition. An aircraft experiences approach conditionswhere descending toward a landing strip to land the aircraft. However,other operability conditions may be suitable for pivoting the airfoil 42to position Y, or to any other positions.

The sensor 52 detects the approach condition and communicates with thecontroller 54 to pivot the airfoil 42 about the pivot mount 60 via theactuator 56. In one example, the sensor 52 detects the approachcondition in response to the opening of the aircraft landing gear. Inanother example, the approach condition is detected in response tosensing a predefined aircraft altitude. In yet another example, theapproach condition is detected in response to sensing a predefinedaircraft airspeed.

In position Y, the fan discharge airflow F1 is forced in a forwarddirection rather than an aft direction of the gas turbine engine 10.Therefore, the airfoil 42 provides a thrust spoiling feature in arelatively inexpensive and non-complex manner as compared to prior-artthrust reversers. The airfoil 42 is returned from position Y to thefirst position X within the pocket 40 where thrust spoiling is no longerrequired by the aircraft.

The foregoing description shall be interpreted as illustrative and notin any limiting sense. A worker of ordinary skill in the art wouldrecognize that certain modifications would come within the scope of thisinvention. For that reason, the follow claims should be studied todetermine the true scope and content of this invention.

1. A core nacelle for a gas turbine engine, comprising a core cowlpositioned adjacent an inner duct boundary of a fan bypass passage,wherein said core cowl includes at least one pocket and at least oneairfoil at least partially received within said at least one pocket,said at least one airfoil selectively movable between a first positionwithin said at least one pocket and a second position that is downstreamfrom said first position to adjust a discharge airflow cross-sectionalarea associated with said fan bypass passage, wherein said fan bypasspassage extends between said core nacelle and a fan nacelle and asecondary airflow passage extends between said at least one airfoil anda core exhaust nozzle where said at least one airfoil is positioned atsaid second position.
 2. The core nacelle as recited in claim 1, whereinthe first position corresponds to a first discharge airflowcross-sectional area and the second position corresponds to a seconddischarge airflow cross-sectional area greater than said first dischargeairflow cross-sectional area, wherein said at least one airfoil isselectively moved to said second position in response to at least oneoperability condition.
 3. The core nacelle as recited in claim 2,wherein said at least one operability condition includes a take-offcondition.
 4. The core nacelle as recited in claim 1, comprising anactuator assembly operable to selectively translate said at least oneairfoil between said first position and said second position.
 5. Thecore nacelle as recited in claim 1, wherein said at least one airfoil ispivotally attached to said core nacelle within said at least one pocketand is positioned adjacent to a fan exhaust nozzle.
 6. The core nacelleas recited in claim 5, comprising a pivot mount at a trailing edge ofsaid at least one airfoil to pivotally attach said at least one airfoilto said core nacelle.
 7. The core nacelle as recited in claim 1, whereinsaid second position is aft of a fan exhaust nozzle associated with saidfan bypass passage.
 8. A gas turbine engine system, comprising: a fannacelle defined about an axis and having a fan exhaust nozzle adjacentan aftmost segment of said fan nacelle; a core nacelle at leastpartially within said fan nacelle, said core nacelle having a core cowlpositioned adjacent said fan exhaust nozzle, wherein said core cowlincludes at least one pocket and at least one airfoil, said at least oneairfoil at least partially received within said at least one pocket andmoveable between a first position having a first discharge airflowcross-sectional area and a second position having a second dischargeairflow cross-sectional area greater than said first discharge airflowcross-sectional area, wherein a fan bypass passage extends between saidfan nacelle and said core nacelle and a secondary airflow passageextends between said at least one airfoil and a core exhaust nozzle whensaid at least one airfoil is positioned at said second position; a fansection positioned within said fan nacelle; a gear train that drives atleast said fan section; at least one compressor and at least one turbinepositioned downstream of said fan section; at least one combustorpositioned between said at least one compressor and said at least oneturbine; at least one sensor that produces a signal representing anoperability condition; and a controller that receives said signal,wherein said controller moves said at least one airfoil from said firstposition to said second position in response to said operabilitycondition.
 9. The system as recited in claim 8, comprising an actuatorassembly in communication with said controller and positioned within acavity of said core nacelle, wherein said actuator assembly isextendable to selectively move said at least one airfoil between saidfirst position and said second position in response to detecting saidoperability condition.
 10. The system as recited in claim 8, whereinsaid operability condition includes a take-off condition.
 11. The systemas recited in claim 8, wherein said second position is aft of said firstposition.
 12. The system as recited in claim 8, comprising a pivot mountthat pivotally mounts said at least one airfoil to said core nacelle,wherein said at least one airfoil is pivoted from said first position toa second position in response to detection of an approach condition,wherein said pivot mount is positioned near a trailing edge of said atleast one airfoil.
 13. A method of increasing a discharge fan airflowcross-sectional area of a gas turbine engine, comprising the steps of:(a) sensing an operability condition; and (b) translating a core cowlairfoil at least partially received within at least one pocket in an aftdirection of the gas turbine engine to adjust the discharge fan airflowcross-sectional area in response to sensing the operability condition;moving the core cowl airfoil from a first position to a second position,wherein the first position corresponds to a first discharge airflowcross-sectional area and the second position corresponds to a seconddischarge airflow cross-sectional area greater than the first dischargeairflow cross-sectional area; providing a secondary airflow passage thatextends between the core cowl airfoil and a core exhaust nozzle inresponse to moving the said core cowl airfoil to the second position.14. The method as recited in claim 13, wherein the operability conditionincludes a take-off condition.
 15. The method as recited in claim 13,comprising the step of: (c) returning the core cowl airfoil to the firstposition in response to detection of a cruise operation.
 16. The methodas recited in claim 15, comprising the step of: (d) pivoting the corecowl airfoil from the first position to a position different than thesecond position to spoil the thrust of the gas turbine engine inresponse to detection of an approach condition.